The present invention relates to a procedure for examining eggs to determine the presence of cracks or holes in the shell through an examination of the elasticity of same.
For many years, a great deal of work has been put into developing suitable methods and apparatus for the automatic detection of so-called cracked eggs, i.e. eggs with cracks or holes in their shells.
Such detection is important for several reasons. One is that the storing quality of such eggs is reduced and their use as food may entail a health risk. Another reason is that damaged eggs cause loss, and irritation in the further handling and distribution of these eggs.
In a number of instances, attempts have been made to base detection on the examination and measurement of several conditions in connection with vibrations or oscillations in the egg shell. Thus, for instance, a method is described in U.S. Pat. No. 3,503,501 whereby a continuously vibrating probe is vibrated against the egg, and the resistance and oscillations, as well as the phase differences between the probe's oscillations and the oscillations produced in the egg's shell during the rotation of the egg are measured. In U.S. Pat. No. 3,744,299 a method is described in which the eggs are rolled over a number of piezoelectric crystals thus receiving energy impulses, and the process consists partly of measuring the energy impulse returned by the eggs and partly the duration of the impulse. The latter process is then used as a gauge for ascertaining the presence of cracks or holes in the shell. Another method is known from U.S. Pat. No. 3,067,605 in which the recoil of light hammers striking passing eggs is measured. Eggs causing a recoil below a certain dimension are defined as cracked eggs.
However, it has been demonstrated that none of these known methods have provided satisfactory results in practice, so one is still obliged to use the familiar method of inspecting the eggs as they pass over a table with a strong light underneath, a method that is both costly because of the wages involved and is also encumbered with the uncertainty involved in such enervating inspection work.